1. Field of the Invention
The invention relates to a startup torque transmitting mechanism of an internal combustion engine, which rotates a crankshaft by transmitting torque from a ring gear to the crankshaft via a one-way clutch during startup.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-A-2003-83216, for example, discloses a startup torque transmitting mechanism of an internal combustion engine, in which a one-way clutch (i.e., a reverse input interruption clutch) is provided between a starter motor and a crankshaft such that the starter motor side can be in constant mesh with a ring gear. In particular, according to the related structure illustrated in page 2 and FIG. 7 of that publication, for example, the ring gear is supported by the crankshaft side via a bearing provided between it and the crankshaft and the one-way clutch is arranged between a reduction gear and a drive gear.
When the bearing and the one-way clutch are both provided in this manner, an oil seal member that seals the inside and outside of the internal combustion engine is particularly important. Because the bearing and the one-way clutch are arranged around the crankshaft in this case, however, the oil seal member must have a large diameter, which means the lip portion of the oil seal member slides at a high rate of speed while the internal combustion engine is operating. As a result, the oil seal member may degrade more quickly.